PHP4 and MySQL database operation functions (3) _ MySQL

7) database information functions (2 functions): 1. mysql_fetch_field () format: objectmysql_fetch_field (intquery, int [field_offset]); 1 object is returned, that is, a hash table marked: table: table name: Field name max_length: maximum length of the field not_null: If the field is notnull, 1 is returned; otherwise, 0 is returned. 7) database information function (2 ):

1. mysql_fetch_field ()
Format: object mysql_fetch_field (int query, int [field_offset]);

Returns an object, that is, a hash table marked:
Table: table name
Name: Field name
Max_length: maximum length of the field
Not_null: If the field is not null, 1 is returned; otherwise, 0 is returned.
Primary_key: If the field is primary key, 1 is returned; otherwise, 0 is returned.
Unique_key: If the field is unique key, 1 is returned; otherwise, 0 is returned.
Multiple_key: If the field is not a unique key, 1 is returned; otherwise, 0 is returned.
Numeric: If the field is numeric, 1 is returned; otherwise, 0 is returned.
Blob: If the field is blob, 1 is returned; otherwise, 0 is returned.
Type: field type
Unsigned: If the field is unsigned, 1 is returned; otherwise, 0 is returned.
Zerofill: If the field is zero filled, 1 is returned; otherwise, 0 is returned.

Reference format: Object name-> subscript name

You can use this function to obtain the table name, field name, and type .......

Example:

$ Query = mysql_query ($ SQL, $ connect );
While ($ object = mysql_fetch_field ($ query ))
{
Echo "table name:". $ object-> table ."
";
Echo "field name:". $ object-> name ."
";
Echo "primary key:". $ object-> primary_key ."
";
Echo "not null:". $ object-> not_null ."
";
Echo "field type:". $ object-> type ."
";
Echo "field max length:". $ object-> max_length ."
";
}
?>

Note: the hash table starts with 0 coordinates, that is, the first field is 0 items in the hash table.
If you want to directly obtain the information of the third field in the hash table, the format is as follows:
$ Query = mysql_query ($ SQL, $ connect );
$ Object = mysql_fetch_field ($ query, 2 );
Echo "table name:". $ object-> table ."
";
Echo "field name:". $ object-> name ."
";
Echo "primary key:". $ object-> primary_key ."
";
Echo "not null:". $ object-> not_null ."
";
Echo "field type:". $ object-> type ."
";
Echo "field max length:". $ object-> max_length ."
";
?>

In fact, this can also be achieved through the following function.

2. mysql_field_seek ()
Format: int mysql_field_seek (int $ query, int field_offset );

Move the cursor to the specified field.
Example:

$ Query = mysql_query ($ SQL, $ connect );
$ Seek = mysql_field_seek ($ query, 2 );
$ Object = mysql_fetch_field ($ query );
Echo "table name:". $ object-> table ."
";
Echo "field name:". $ object-> name ."
";
Echo "primary key:". $ object-> primary_key ."
";
Echo "not null:". $ object-> not_null ."
";
Echo "field type:". $ object-> type ."
";
Echo "field max length:". $ object-> max_length ."
";
?>

This also meets the same requirements as the above example.

8) database name and table name (2 ):

1. mysql_list_dbs ()
Format: int mysql_list_dbs (int link_identifier );
Obtain the names of all available databases ).

Example:

$ Connect = mysql_connect ($ host, $ usr, $ pwd );
$ Dbs = mysql_list_dbs ($ connect );
$ Rows = mysql_num_rows ($ dbs );
Echo "database total:". $ rows;
$ I = 0;
While ($ I <$ rows)
{
$ Db_name [$ I] = mysql_tablename ($ dbs, $ I );
Echo $ db_name [$ I];
$ I ++;
}
?>
The names of all databases in MySQL are displayed in sequence ).
Note: it is equivalent to the show databases command in MySQL.

2. mysql_list_tables ()
Format: int mysql_list_tables (string database name );
Displays the names of all tables in the database.

Example:

$ Connect = mysql_connect ($ host, $ usr, $ pwd );
$ Tables = mysql_list_tables ("mysql ");
$ Rows = mysql_num_rows ($ tables );
Echo "Table total:". $ rows;
$ I = 0;
While ($ I <$ rows)
{
$ Table_name [$ I] = mysql_tablename ($ tables, $ I );
Echo $ table_name [$ I];
$ I ++;
}

?>

The names of all tables under mysql are displayed in sequence.
Note: it is equivalent to the show tables command in MySQL (first use the use mysql command to select a database)

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